In the field of packaging materials, polyesters have rapidly developed in recent years. In particular, polyethylene terephthalate (PET), by a process of stretch-blowing preforms, has shown a remarkable aptitude for fabrication of bottles with excellent mechanical properties (notably shock resistance and resistance to internal pressure), allowing for their advantageous usage in the packaging of pressurized liquids such as carbonated beverages. However, occasionally when dealing with highly flavored liquids and/or oxygen sensitive liquids and/or carbonated liquids, the packaged product is deficient from the standpoint of preservation where the polyethylene terephthalate hollow bodies are not sufficiently gas or flavor impervious. This is even more so when the body wall is thin and when the ratio of the surface of the receptacle to the volume of the contents is significant. See, for example, U.S. Pat. Nos. 3,733,309 and 4,267,143.
It is also known in the art that polymers such as PET can be laminated to EVOH to improve the gas barrier properties of these polymers. See, for example, U.S. Pat. No. 3,595,740. It is also known in the art that blends of PET and EVOH are useful in making containers having good gas barrier properties.
Other patents of interest in this field are G.B. Pat. No. 1,545,096 and U.S. Pat. Nos. 4,261,473; 4,282,671 and 3,585,177.
It is not believed to be known that biaxially oriented monolayer containers produced from PEN blended with up to about 30 wt % EVOH (based on the combined weight of PEN and EVOH) would result in unexpectedly low oxygen permeability when compared to such containers produced from PET and EVOH.
PEN is useful for producing monolayer biaxially oriented containers having good barrier against oxygen (O.sub.2), carbon dioxide, and water vapor permeation. PEN may be processed by injection stretch blow molding (single stage) or reheat stretch blow molding (two stage) to produce a variety of container shapes having about 1.5 cc mil/100 in.sup.2 -24 hr at 30.degree. C. and 68% RH oxygen permeability (1.5 PU) and 0.90 g mil/100 in..sup.2 /24 hr at 100.degree. F. and 90% RH (TR) Water Vapor Transmission Rate (WVTR). Using the polymer blends of the present invention, the O.sub.2 barrier of these containers can be reduced to about 0.10 PC while maintaining the WVTR to about 0.9 TR. PU, or permeability unit, is defined as the number of cc's of gas permeating a 1-mil thick sheet of 100 in..sup.2 in 24 hr at 30.degree. C. and 68% relative humidity. TR is defined as number of grams of water vapor permeatig a 1-mil thick sheet of 100 in..sup.2 in 24 hr at 100.degree. F. and 90% relative humidity.
The improveemnt in gas barrier properties is attained without sacrificing physical properties of containers, and the containers produced by this process result in an attractive pearlescent appearance.